The present invention relates to a transmission convergence sublayer multiplex generating/terminating apparatus and, more particularly, to an ATM switch accommodating a plurality of low-speed lines, an interface between an ATM switch and an SDH (Synchronous Digital Hierarchy) transmission equipment, and the like.
A conventional apparatus which accommodates an ATM layer information input line, generates ATM transmission convergence sublayers (to be referred to as TC layers hereinafter) for m VC11 paths, and generates an STM1 highway by STM-multiplexing the VC11 paths, will be described below with reference to FIG. 5.
FIG. 5 shows a conventional STM1 generating apparatus.
An STM1 generating apparatus 300 is constituted by an SDH generating section 310, TC layer generating sections 320-i (1.ltoreq.i.ltoreq.m), and an ATM layer distributing section 330. The TC layer generating sections 320-i are respectively constituted by TC layer information registers 322-i, and ATM layer information registers 323-i.
An ATM layer information input line ATMin is connected to the ATM layer distributing section 330. The ATM layer distributing section 330 is connected to data input lines Di-i. The data input lines Di-i are respectively connected to the TC layer calculating sections 321-i of corresponding numbers i. The TC layer calculating sections 321-i are respectively connected to data output lines Do-i and control lines C-i of the corresponding numbers i. The data output lines Do-i and the control lines C-i are connected to the SDH generating section 310. The SDH generating section 310 is connected to an STM1 highway output line STM1out.
The ATM layer distributing section 330 analyzes the multiplex identifiers of ATM cells received from the ATM layer information input line ATMin, and distributes the respective cells to the data input lines Di-i corresponding to the path numbers. The TC layer generating sections 320-i store the ATM cells, which have been received through the data input lines Di-i of the corresponding numbers i, in the ATM layer information registers 323-i. If there is an empty space in a given TC layer information register 322-i, the corresponding TC layer generating section 320-i generates TC layer information by using the ATM layer information at the head of the corresponding ATM layer information register 323-i, and stores the TC layer information in the TC layer information register 322-i. Upon detection of a TC layer information output request from the SDH generating section 310 to a given control line C-i, the corresponding TC layer generating section 320-i outputs the TC layer information extracted from the corresponding TC layer information register 322-i to the corresponding data output line Do-i.
The SDH generating section 310 outputs a TC layer information output request to each control line C-i in accordance with the time position information of each path on an SDH frame, maps the pieces of TC layer information of the respective paths which have been received through the respective data output lines Do-i onto an SDH path, and outputs the mapped data to the STM1 highway output line STM1out.
A conventional apparatus which accommodates an STM1 highway obtained by STM-multiplexing m VC11 paths onto which ATM cells are mapped, and terminates the TC layers of the respective VC11 paths will be described next with reference to FIG. 6.
FIG. 6 shows a conventional TC layer terminating apparatus.
A TC layer terminating apparatus 400 is constituted by an SDH terminating section 410 and TC layer terminating sections 420-i (1.ltoreq.i.ltoreq.m). The TC layer terminating sections 420-i are respectively constituted by TC layer calculating sections 421-i and TC layer information registers 422-i.
An STM1 highway input line STM1in is connected to the SDH terminating section 410. The SDH terminating section 410 is connected to data input lines Di-i and control input lines Ci-i. The data input lines Di-i and the control input lines Ci-i are respectively connected to the TC layer calculating sections 421-i of corresponding numbers i. The TC layer calculating sections 421-i are respectively connected to data output lines Do-i and control output lines Co-i of the corresponding numbers i.
The SDH terminating section 410 terminates each VC11 path of the STM1 highway input line STM1in. The SDH terminating section 410 then outputs the CT layer information extracted from each VC11 path to the data input line Di-i corresponding to each path number in units of bytes, and indicates through the corresponding control input line Ci-i that the output information is valid. Each TC layer information register 422-i holds the latest TC layer information of the path, which has been received from the SDH terminating section 4101, by five bytes in the order of arrival.
As known well, cell synchronization as termination of a TC layer and a cell scrambler can be calculated for each byte data. When a given TC layer calculating section 421-i detects a validity indication on the corresponding control input line Ci-i, the TC layer calculating section 421-i terminates the TC layer by using a total of 6-byte TC layer information, i.e., the TC layer information received through the corresponding data input line Di-i at the same timing as that of the detection and 5-byte TC layer information held in the corresponding TC layer information register 422-i, generates ATM layer information, and outputs it to the corresponding data output line Do-i. At the same time, the TC layer calculating section 421-i writes the received TC layer information in the TC layer information register 422-i to update its contents.
In the conventional techniques, since a TC layer is generated or terminated by a circuit arranged for each path of an STM highway, hardware for generating or terminating TC layers is required by the amount corresponding to the number of paths. If a large number of paths on the STM highway are to be accommodated, the hardware amount becomes large.